3-D Movies Like 'Alice in Wonderland' Are Just a Headache for Some

March 2, 2010— -- Movies and television shows in 3-D have become trendy, but they spotlight the problems some people have watching them. Some people feel discomfort; others can't see the 3-D effect at all.

Johnny Depp, who plays the Mad Hatter in the upcoming 3-D feature "Alice in Wonderland," says he avoids watching all his films, but in an interview with Entertainment Weekly he said he had a special excuse this time, since he can't enjoy the 3-D effects.

"I've got a weird thing where I don't see properly out of my left eye, so I truly can't see 3-D," he told the magazine.

Depp is far from alone in his troubles with the third dimension. Exact numbers are hard to pin down, but studies have estimated that between 5 percent and 12 percent of Americans have some degree of stereoblindness, which is the inability to see depth properly.

"I don't sense that I'm looking at a 3-D image," said Rafe Needleman, an editor at the technology Web site CNET. "It's far more tiresome than convincing, because mostly, I see double images or ghosting. Either it doesn't work and I don't see anything, or I see two images where I know I should see one."

Three-dimensional films are constructed by using two cameras set slightly apart from each other. That's why, if you look at a 3-D film without the glasses you receive at the theater, you can see two separate images. Using the glasses, however, helps the brain consolidate the images, giving the picture depth.

"In life, that's what's happening. That's what fusion and stereopsis are," said Dr. Lisabeth Hall, a pediatric ophthalmologist at New York Eye and Ear Infirmary, naming the process by which the brain consolidates images from the two eyes to create depth perception.

The fine depth perception used for 3-D films, as well as tasks like flying a plane or constructing a top-quality Swiss watch, is not the only depth perception the brain can generate from information the eyes give it. Even with one eye, the brain can figure out how far away certain objects are.

"The brain can make judgments about depth from many different clues," said Dr. Joseph Rizzo, a neuro-ophthalmologist at the Massachusetts Eye and Ear Infirmary and Harvard Medical School.

There are a number of reasons why someone might not be able to enjoy the full effect of a 3-D film. Doctors told us that for optimal stereo vision, two factors have to come together:

First, both eyes must have good vision on their own.

Second, the eyes must be aligned and have developed together. If an eye drifts during childhood, a child might not have depth perception.

Viewing In Stereo

Hall said difficulty in watching a 3-D movie might be because of a subtle misalignment of the eyes, even though the person has perfect vision in everyday life. She also said that children, parents and adults experiencing difficulty with the 3-D experience shouldn't panic but should consider getting evaluated, since even with current aggressive screening, children's eye problems can be missed.

"Get it evaluated, get it diagnosed, but it's not worth worrying about," she said, explaining that some adults might have had subtle vision problems they've lived with their whole lives without noticing them. People can have varying degrees of ability when it comes to seeing depth, and some adults and children who do have vision problems in the clinic can still enjoy 3-D movies.

"Very often, kids or adults who can't test positively on the stereo testing that we have will report this sense of depth," said Hall. "It's not a black and white answer."

Rizzo said that if a person could see 3-D movies without difficulty, and then suddenly lost the ability, that might be a sign of a potential problem.

"People may develop a variety of problems that limits their vision," he said. "In that situation, dealing with the cause of the reduced vision would restore visual function."

A number of features have been shown in 3-D recently, including "Avatar," an NFL game between the San Diego Chargers and Oakland Raiders this past season, and some commercials aired during last year's Super Bowl.

Needleman said that while the industry may want to go forward with 3-D television sets and other technology that captures these images, they may want to think about the people who can't appreciate it.

How important are "the people with stereoblindness to people who are in the 3-D industry? What are they going to do for us? How are they going to deal with the social division?" he said, referring to instances in which someone who can't see 3-D effects goes to a movie with people who can.

A Different Viewing Experience

Can eye exercises restore depth perception? Doctors say no treatment has so far been accepted as one that works in large numbers of people.

Needleman, the CNET editor who cannot see 3-D effects, said it worked to his advantage. He said he enjoyed seeing "Avatar" in 2-D -- and avoided the crowds who wanted to see the more heavily promoted 3-D version.

"3-D adds to the spectacle, but I don't think it adds to the story," he said.